<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .top {
      float: left;
      width: 0;
      height: 0;
      border-top: 100px solid red;
      border-left: 100px solid transparent;
      border-right: 100px solid transparent;
      border-bottom: 100px solid transparent;
    }

    .left {
      float: left;
      width: 0;
      height: 0;
      border-top: 100px solid transparent;
      border-left: 100px solid yellow;
      border-right: 100px solid transparent;
      border-bottom: 100px solid transparent;
    }

    .right {
      float: left;
      width: 0;
      height: 0;
      border-top: 100px solid transparent;
      border-left: 100px solid transparent;
      border-right: 100px solid pink;
      border-bottom: 100px solid transparent;
    }

    .bottom {
      float: left;
      width: 0;
      height: 0;
      border-top: 100px solid transparent;
      border-left: 100px solid transparent;
      border-right: 100px solid transparent;
      border-bottom: 100px solid green;
    }

    .left-top {
      float: left;
      width: 0;
      height: 0;
      border-top: 100px solid yellow;
      /* border-left: 100px solid green; */
      /* border-bottom: 100px solid transparent; */
      border-right: 100px solid transparent;
    }
  </style>
</head>

<body>
  <div class="top"></div>
  <div class="left"></div>
  <div class="right"></div>
  <div class="bottom"></div>
  <div class="left-top"></div>
</body>

</html>